A little late - A good math teacher is someone who has a passion for mathematics and can share and instill that passion upon their students.
Good math teachers/professors should be the ones who encourage their students to go beyond the classroom with their learning. They should encourage and help their students get involved in original research and advise them on what steps to take. The teachers have the experience and the students do not; thus, the teachers should share this experience with their students.
A good math teacher is one that teaches students what the true joy of mathematics is and how to function in a world outside school utilizing mathematics.